Manufacture of rubber and the like



Patented Sept. 4, 1928.

UNITED STATES PATENT OFFICE.

PHILIP SOHIDROWITZ, LONDON, ENGLAND, ASSIGNOR TO VUL'I'EX LIHITED, OI JERSEY, CHANNEL ISLANDS, ENGLAND, A JERSEY COMPANY.

MANUFACTURE OI RUBBER AND THE LIKE.

1T0 Drawing. Application filed larch 14, 192?, Serial No. 625,171, and in Great Britain September 14, 1922.

The present invention is for improvements in or relating to the manufacture of caoutchouc compositions.

In my U. S. patent spec1ficat1on No. 5 1,443,149 I have described the manufacture of vulcanized rubber compositions by submitting latex in the uncoagulated state to vulcanization with sulphur or other vulcanizing agent under such conditions as to preclude coagulation, or any substant1al coagulat1on of the rubber during vulcanization. The present-invention consists in a mothfication of the process of the aforesaid specific ation, and is characterized essentially by vulcanizing the latex-mixing under the conditions prescribed at a temperature below that ordinarily employed in hot methods of vulcanization.

In the case of the present invention, therefore, as in that of specification N 0. 1,443,149, latex is vulcanized without prior coagulation of the caoutchouc, and under conditions preeluding this change during the vulcanization. To render the rocess reasonably expeditious, the latex-mixing preferably comprises an active accelerator of vulcanization. The nature and the pro ortion employed of such accelerator are dlipendent upon circumstances, such as the composition of the vulcanizable mixing, the condition or concentration of the latex and the nature of any preservative present therein, but the condi-.

tions of operation in any given case may be readily determined by a simple preliminary trial. A nitrogenous organic base, such as iperidine derivatives, for instance, in the orm of the accelerator prepared according to U. S. patent specification No. 1,418,976, may advantageously be utilized. The invention is, however, not limited in respect to the use of a particular accelerating agent, and I have found that active accelerators, whether water-soluble .or not, may be employed.

The vulcanizable mixing may be left to beheated at that of the water-bath or at a suitable temperature below the usual boiling-point of water, until vulcanization has menced at a substantially normal temperature, for instance, at about 15 (3., and the been efi'ected; or the process may be com-.

vulcanization completed by subsequent application of heat within the limit aforesaid.

.The presence of rubber coagulants in the vulcanizable latex-mixing is to be avoided, and in order to prevent coagulation during the vulcanization the latex or other caoutchouc containing material ma be rendered definitely alkaline or definite y basic prior to treatment. It is preferred to work with definitel alkaline or definitely basic mixings, alt ough with fresh latex uite a low degree of alkalinity may sufiice an may even not be necessary in certain cases when the latex displays little tendency to coa lation.

By definitely alkaline or efinitely basic is meant either alkaline or not acid to an appropriate indicator which, of course, will be selected according to the reagent employed for providing the basicity of the mix- [he latex ma bev rendered alkaline or basic by the ad ition of ammonia, or like base, or of a sufficiency of an accelerator such as piperidine, or the alkali may be a compopartly or wholly separates from the aque" ous reaction-1nixture in a coalesced (but not coagulated) form, or a solution or com -parable colloid suspension of the vulcanized product in water may be obtained, according to the conditions of working, for instance,

the composition of the mixing or the manner of vulcanization. stand at the ordinary temperature, or may The vulcanizedproduct may be separated from the reaction mixture by any desired method, for example, by evaporation of the liquid after straining if required, or by ad dition to the liquid of coagulants, for instance, a suitable salt such as Epsom salts (e. g. 5 15 per cent 0i a 20 per cent.

' b n s p vcase of ordinary (unvulcan crepe or sheet, or other form of raw rubber derived from the original one lum. I

Fibrous and ot er fillers or ents, dyes or other compoundmg materi may be added at any suitable of the process.

vulcanized roduct in coalesced form, or the vulcanized quid may be applied to fabrics, paper, woven fibres 'suchas ropes, cords; threads, nets or the like, by spreaddipping or other operations as to the nature fabrics, fibres uently dried convement accordin of the material suchtrea or other material being su wholly or partaliy anysuitab e method of evaporation.

gulanls may be used but as'a rulearenotny.

When wholly or partly dried the treated material may be washed with wateror with a dilute aqueous acid for the purpose of improving the finish or a dilute alkali may beemplo ed, according to the nature of the rubber-fihn or the material upon which it is deposited.

' Alternativel or in combination with the fore ing w g with water or acid or Elk e solutionsbg the dry sull lstantlilally ry s may t oug or ave apphed to them a ute solution of a gelforming substance, preferably under slight application of heat. For exam lo, the goods may-be treated with a warm lute aqueous solution of] gelatine; or agar-agar '(say 0,254.0 per cent strength), a treatment which facilitates handling of the goods andhas arotective action u 11 their surfaces, as we milled, d

as assisting to prove thefinish. The following examples will indicate-how the invention may be carried into effect, and:

'ared accordingto the specification of U. S. atent No. 1,418,976, this accelerator con-. sisting of zinc pxide c g about'6 per cent of piperidyldithiocar mate of piperiine. r

The mixing was allowed to stand at the ordinary temperature,-about; 0., during three days, at the end of which time the whole had coalesced to a thickened mass, the solids of which consisted of a vulcanized rubber composition. Ewdmpk II.

.7 To 200 cc. of latex containing 30 per cent of rubber and dpieserved with 1 per cent of ammonium by to there was added a cream made by mixing 15 to20 cc. of water with 3 Example I, 6 of sulphur and 3 grams of zinc oxide. The mixing was allowed to stand for aboutthree days at the ordinary tem rature durin which period slight thic ening took p ace. The mixing was then. transferred to a flask which was immersed in a boiling watenbath. After about 2 to 3 hours there was obtained a coalesced mass of vulcanized rubber.

A mixing prepared according to Example II was left to stand for five da at ordinary temperature. At the end of t 's period the mixing displayed slight thickening, but was perfectly mo ile and gave no evidence either of coagulation or coalescence. After straining to remove'zinc oxide, excess sulphur and accelerator, application of the usual tests to the rubber obtained. from the strained fluid showed this rubber to be in thevulcanized condition.

Ezhample IV.

grams ofthe same accelerator given in To 2000 cc. of 1atex,,containing 30 per cent of rubber and preserved with 1- per cent of ammonia, there was added a cream composed of 40 grams of sulphur, 20 x s of zinc oxide, 6 grams of the carbon blsulphide derivative of di-ethylamine, and 150 cc. of water, slightly alkaline with ammonia. After agitation for a brief period in order to disperse, the cream, the mixing was leftto stand for four days at room temperature,

it will be appreciated that these examplesif gwith agitation once-0r twice a day. No a are furnished for illustrative purposes and cent of rubber,'admixedwith'a solution'of sodium'polysulphide, assaying about 25 per cent of precipitable sulphur, 1n the proportionof 1"part of thesulphide solution to 12 parts of the latex, were added, in the form of a cream made with about 20 cc. of water, .iflgrams of: an accelerator prepreciable thickening of the mixing was 0 servable at theend of this period. The

reactionmixture was perfectly mobile and gave no evidence'either of coagulation or of coalescence. After straining to remove zinc Joxide, excess of sulphur and'accelerator application of the usual tests to the ra her from the stained fluid showed this rubber to be in the vulcanized condition.

A mixing prepared according-to Example IV was heated for 30 minutes at 70 C. (after a rise of about to minutes). The

Exam le VI.

A mixing pre ared and treated according to Example I with the exce t1on, of the replacement of the fi-grams o the carbon was no evidence or either coagulation or derivative 'of piperidine, was -foun bisulphide derivative of di-ethylamine by the same weightofthe carbon bisul hide on standing to thicken slightly, although there coalescence. The mixing was left to stand for four days, and was then strained. Ap-

plication of the usual tests to' the rubber showed the latterto be vulcanized. "Indeed in this case a slightly overvulcanized prod- 1 not was obtained.

Emample V11.

' A mixing repared and treated according to Example with the exception of the substitution of the piperidine derivative of carbon bisulphide for the corresponding derivative of diethylamine, also displayed slight thickening but without coagulation or coalescence. After straining, examina-- tion in theus'ual way showed the rubber to be a fully vulcanized product.

Example VIII.

sulphide derivative oi piperidine, and 1 grain of zinc oxide in-the form of zinc hydrate in solution in slight excess of am-- monia. This mixing was left to stand at a low room temperature (440 C.) for about twelve hours, and then after straining was divided into two portions. One portion was coagulated by addition of dilute acetic acid, and the other portion was evaporated to dryness at a temperature of about 25 C. Application of the usual tests to the washed and dried coagulum and to the residue ob tained by evaporation proved both products to consist of well vulcanized rubber.

It will be observed in the above example that only about half a day was required for the vulcanization although the temperature 'at which this change was eiiected was unusudivision in order to e dite the vulcanization provided that the quantity of the promoter in the reaction-mixture proportionately to the vulcanizing agent be not so great as to induce coagulation during the vulcanizing process. '.Thus, if with a given mixin coagulation sets in, the quantity of t e promoter must be reduced, or the relative proportions of promoter and vulcanizing agent readjusted, but with any given ,new mixing such adjustment of relative quantities is a matter for simple pre- 'l1minary trial. In the cas of zinc oxide. the

increased accelerating eiiect referred to becomes noticeable with a state of sub-division finer than that of the commercial product usually employed and such finer state of divisition is apparently most advanta eously of the order of collold dimensions 0 particle, such, for example, as may reasonably be expected exist in a solution of the hydrate of this metal in an alkali.

In the preparation or rubber compositions by direct vulcanization of uncoagulated latex, the danger of fire and the toxic eifects associated with the use of the usual rubber solvents are avoided, and these advantages attach not only to the process of manufacture of'the composition but also to the applications of the vulcanized product. For

example, in the impregnation or coating of fabrics drying may be effected beforenn open fireif desired. A further advantage is that the odour, it any, 'of the residue ohtained by evaporation of the vulcanized latex. is unobjectionable, whereas a certain peculiar odour is almost always left on'evaporation of solutions of rubber in the usual commercial solvents. The low temperature vulcanization characteristic of the present invention constitutes a process of manufacture both economical and simple in operation in that pressure-heating or closed vessels need not be employed, with consequent simplification and saving of plant, together with ease and simplicity of Working and economy in heat energy. In addition, pr ducts cured at low temperatures in presence of an active accelerator according to this invention are in general tougher and age better than products obtained by the hot cure of rubber as usually practiced, a superiority comparable in these respects. to that displayed by products prepared by a short hot cure wit an active accelerator over those obtained by long ordinary hot vulcanization. I claim: A

1. The process for the manufacture of vul canized compositions which comprises substantially uncoagulated caoutchouc at a, temperature below those ordinarily employed in hot vulcanizing methods under such conditions as to preclude any substantial coagulation of the caoutchouc during the vulcanization.

lated caoutchouc urinf the vulcanization. or the manufacture of vulcanized compositions'which comprises vulcanizing "a vulcanizable plant --latex at a temperature'below thoseordinarily em loyed in hot vulcanizing methods under suc conods under suc ditions as; to preclude an agulation of the vuloaniza le material dur- '11. The process for the substantial coin; the vulcanization. v t 4. The.p rocess for the manufacture of vulcanized rubber compositions which comprises vulcanizing substantially .uncoaguated rubber latex at a temperature below those ordinarily employed in hotvulcanizing methods under such conditions as to preelude any substantial coagulation of the rub-- ber during thevulcanizatlon.

. 5. The rocess for'the manufacture of vulcanized ru ber compositions which comprises vulcanizing substantially uncoagulated rubber latex in presence of an accelerator of vulordinarily in hot .vulcanizing methods under so any substantial'fcoagulation of the duri the vulcanization.

6. he processfor the manufacture of vulemployed canized rubber compositions which comprises vulcan'izing' substantiall uncoagu lated rubber latex :in presence '0 *an'accelerator -of;"vulcanization and a promoter for said accelerator at atemperatur'e below those ordinarily em loyed in hot vulcanizing meth- I 7 h conditions as to preclude any substantialcoagulation of the rubber during the vulcanization.

'7. The process for the manufacture of vulcanized rubber compositions which com-. prises Vulcan prises vulcanizij substantially uncoagu lated rubberlatexjm an alkaline condition in presence of anjaccelerator of vulcanizationand a'pr'omoter'for said acceleratorat a temperature below tliose, ordinarily employed in hot vulcanizin Ifiethodsunder such conditions as to prec ude an substantial'coa'gulaated ammomcal rubberlatex 1n presence of an accelerator of vulcanization at-a tem- 9. The procem 'for the manufacture of vul'-' canized rubber compositions which comrises vulcani colloid, at

' Yprises vulcanizing conditions as topreclude,

rubber- A a lated rubber latex-man alkalinecondition substantially uncoagulated rubber latex in an alkaline-condition h substantially uncoagu hot vulcanizing methods. ated. rubber latex 'i'njan alkaline condition f in presence-ofan ecoelerator of vulcaniza h d r yloy in methods under suclrrconditiona as to precl any substantial coagulation of the .rubber' during the vulcanization,

10. The'process for. the of .frulcanized rubber com H tions which combt uncflgulated'rubber latex alkalinz gmdifion in. presence of an accelerator of and'of colloidal-zinc ox de at a. tem

below those ordinarilyemployed in ot vul-. canizing methods under such conditions as to preclude any substantial coagulation"!!! the rubber during the vulcanization, I

manufacture of vulcanized rubber compositions which comrises. vulcanizing su tiall .J ated rubber latex in presence o ator of vulcanization at a tem bea 'tem low C. under such con tions' as to preclude any substantial coagulation of the rubber during the vulcanization.

12., The process for the of vulcanized rubber com o tions which comprises vulcanizing sutially uncoagulated. rubber latex in an condition in presence of an accelerator of vulcanization at a temperature below 100. C. f

13. The process for the manufacture of vulcanized rubber coin 'tions comprises vulcanizing su tially uncoaguprises vulcanjz' rtially uncoagulated rubber latex man alkaline condition in presence of an acceleratorof; vulcanization and of colloidal zinc oxideat a tially constant temperature. below 100 C. under such conditions as to preclude an substantial coagulation of the rubberuring .the vulcanization.

,16. The process for themanufadure of vulcanized rubber compositions which comrises valcanizing substantially uncoagu- 'perature below these ordinarily employed in l'LtThe processsfor the manufacture of prises vulcanizing substantially uncoagulated rubber latex with an alkaline vulcan zing agent in presence of an accelerator of vulcanization at a temperature below those ordinarily employed in hot vulcanizing methods.

18. The process 'for the manufacture of vulcanized rubber compositions which comprises vulcanizing rubber latex in an alkaline condition in presence of an accelerator at vulcanization at a temperature below those ordinarily employed in hot vulcanizing methods, embodying the vulcanized product with a solid material and evaporating the liquid to deposit the vulcanized rubber upon said material.

19. The process for the manufacture of vulcanized rubber compositions which com-" prises vulcanizing substantially uncoagubodying the vulcanized product with a solid material, evaporating the liquid to depositthe rubber u on said material, and treating the su stantially dried rubberized product with a dilute solution of a gelforming substance.

21. The process forthe manufacture of,

vulcanized rubber compositions which comprises vulcanizing substantially uncoagulated rubber latex in an alkaline pondition in presence of an accelerator of vulcanization at a temperature below those ordinarily employed in hot vulcanizing methods, embodying' the vulcanized product with a solid material, evaporatin the liquid to deposit the rubber upon sai material, and treating the substantially dried rubberized product with a dilute solution of gelatine.

' 22. The process for the manufacture of vulcanized rubber compositions which comprises vulcanizing substantially uncoagulat ed'rubber latex in an alkaline condition in presence of an accelerator of vulcanization at a temperature below those ordinarily employed in hot vulcanizing methods, embodying the vulcanized product with a solid ma- Ill) terial, evaporating the liquid to deposit the,

rubber upon said material, washing the.

substantially dried rubberized product and treating the washed product with a dilute solution of gelatine.

23. A vulcanized aqueous substantially un- T coagulated .caoutchouc suspension vulcanized without substantial coagulation of the caoutchouc'at a temperaturebelow those ordinarily employed in hot vulcanizing methods.

24. Vulcanized substantially uncoagulated 7 rubber latex vulcanized without substantial coagulation of the rubber at a temperature below those ordinarily employed in hot vulcanizing methods;

' 25. Vulcanized substantially uncoagulated coalesced rubber.

26. An article formed with vulcanized rubber prepared by vulcanization of substantially uncoagulated rubber latex at"a temperature below those ordinarily employed in hot vulcanizing' methods v v 27. An article formed with vulcanized rubber compounded with a filling material and prepared by vulcanization of substantially 'uncoagulated rubber latex at a temperature below those ordinarily employed in hot vulcanizing methods. v

28. An article formed with vulcanized rubber compounded with a fibrous filling material and prepared by vulcanization of substantially uncoagulated rubber latex at a temperature below those ordinarily employed in hot vulcanizing methods.

'29. A process for manufacturing a fluid vulcanized caoutchouc composition which comprises mixing vulcanizing ingredients with an aqueous dispersion of rubber in the presence of an alkaline preservative. and agitating the mass at a temperature below approximately 212 F. until an aqueous dispersion of vulcanized rubber is obtained.

In testimony whereof I aliix my signature.

PHILIP SCHIDROWITZ. 

